Facebook has acquired Push Pop Press, a start-up that converts books into iPad- and iPhone-friendly formats.

“Until a few years ago, hardly a day would go by in the summer without the mailman bringing a postcard from a vacationing friend or acquaintance. Nowadays, you’re bound to get an email enclosing a photograph, or, if your grandchildren are the ones doing the traveling, a brief message telling you that their flight has been delayed or that they have arrived.”